As a neutral fertilizer, urea is suitable for all kinds of soils and plants. Easy storage, convenient use and little damage to soil. It is a chemical nitrogen fertilizer with large usage and the highest nitrogen content. Urea is synthesized from ammonia and carbon dioxide in industry under certain conditions.
Chinese name
Urea [9]
Foreign name
Urea [9]
Another name
Urea, Carboxamide [9]
chemical formula
CH4N2O or CO (NH2) 2 [8]
molecular weight
60.06
Reading expert? Pu Fuyong
Urea (urea), also known as urea and formamide, has the chemical formula of CH4N2O or CO(NH2)2[8], is an organic compound composed of carbon, nitrogen, oxygen and hydrogen, and is white crystal. One of the simplest organic compounds is the main nitrogen-containing end product of protein metabolism in mammals and some fish.
As a neutral fertilizer, urea is suitable for all kinds of soils and plants. Easy storage, convenient use and little damage to soil. It is a chemical nitrogen fertilizer with large usage and the highest nitrogen content. Urea is synthesized from ammonia and carbon dioxide in industry under certain conditions.
Atomic group refers to the atomic group that participates in chemical reactions as a whole. An atomic group is a part of a molecule. In compounds composed of three or more elements, molecules usually contain some kind of atomic group. Charged radicals are also called free radicals, such as OH-, NO3-, CO32-, SO42-, ClO3-, PO43-, HCO3- and NH4+.
Chinese name
radicle
Foreign name
radicel
Another name
Root and group
subject
chemistry
Charged radicals are also called free radicals or groups, such as OH- hydroxyl, NO3- nitrate, CO32- carbonate, SO42- sulfate, ClO3- chlorate, PO43- phosphate, HCO3- bicarbonate and NH4+ ammonium. It is worth noting that the atomic group cannot exist independently, but is only a component of the compound. In solution, atomic groups participate in the reaction as a whole. All kinds of atomic groups have their own characteristic reactions, for example, CO32- turns into CO2 in acid, SO42- turns into Ba2+ to produce white precipitate insoluble in dilute nitric acid, and OH- turns phenolphthalein test solution into red. The existence of roots can be tested by characteristic reaction. Pay attention to distinguish manganate MnO42- and permanganate MnO4-, which have the same composition, but the valence state of manganese is different, so the root valence is different. Manganese in manganate is +6, and manganese in permanganate is +7. There are also metaphosphate PO3- and phosphite PO33-, in which the former phosphorus is +5 and the latter phosphorus is +3. The valence of an atomic group is equal to the algebraic sum of valence of each element in the root [1].
trait
The unique properties of atomic clusters come from their structural characteristics. Because of their small size and high atomic ratio on the surface, the geometric configuration, spin state and interatomic force of the surface atoms are completely different from those of the bulk phase. The properties of materials are closely related to the surface properties of internal units. For example, only by adjusting the size of clusters, the material properties are very different. The efficiency of clusters with 10 iron atoms in catalyzing ammonia synthesis is 1000 times that of clusters with 17 iron atoms [2].
Another effect brought by size is quantum effect. The study of atomic clusters has proved many hypotheses and predictions of quantum mechanics, and also raised countless more interesting new questions. For example, in a polyhedral cluster composed of pure metal atoms, the structure is stable only when the number of atoms is "magic number sequence", and it will not be destroyed even if it is heated to liquid state. The same "magic number series" has long been known in the periodic law of elements, but its theoretical explanation is still inconclusive.
The scientific research of cluster is in the stage of vigorous development. In addition to great theoretical significance, the practical application of atomic clusters in sound, electricity, light and magnetism is the direction of people's efforts.
Pay attention to understanding
The (1) atomic group is a part of a molecule. In compounds composed of three or more elements, molecules usually contain some kind of atomic group [3].
(2) In any chemical reaction, the atomic group will not remain unchanged. In some chemical reactions, atomic groups will change, for example, chlorate in potassium chlorate will change during the reaction.
(3) Atomic groups are usually called "roots" or "root ions". When writing the symbol of atomic group, the charge it carries should be indicated, such as ClO3-, SO42-, OH-, NH4+, etc. Don't mistake the symbol of atomic group for chemical formula, such as mistaking sulfate radical (SO42-) for sulfur tetroxide.
Corresponding substance
Acid and salt
Most atomic groups [4] are acid groups. If you want to turn it into the corresponding acid, you usually need to add a corresponding number of hydrogen atoms before the acid radical. If nitrate NO3- becomes nitric acid, it is HNO3, and sulfate SO42- becomes sulfuric acid, it is H2SO4. In addition to adding metal or ammonium before acid radical, so is salt.
Organic acid radicals become organic acids or corresponding salts. When writing chemical formulas, it should be noted that hydrogen or metal is written before acid radical.
alkali
Alkali is a metal element added before hydroxyl OH-
ammonia
Ammonium is special. Because its valence is+1, it becomes the corresponding substance by removing a hydrogen to become ammonia NH3.
cyanogen
Cyanide is also special. Cyanide is CN-, and the chemical formula of cyanide is (CN)2.
Valence of atomic group
+1 price
Ammonium: NH4[5]
-1 price
Hydroxyl: OH nitrate: NO3 nitrite: NO2
Bicarbonate: HCO3 bisulfate: HSO4 bisulfite: HSO3
Metaphosphate: PO3 chlorate: ClO3 perchlorate: ClO4
Chlorite: ClO2 hypochlorite: ClO dihydrogen phosphate: H2PO4
Bromate: BrO3 perbromate: BrO4 iodate: IO3.
Periodate: IO4 potassium permanganate: MnO4 cobaltate: CoO2
NiO _ 2: NiO _ 2: Re _ O _ 4: HCOO
Acetate: CH3COO cyanide: CN thiocyanate: SCN
-2 valence
Carbonate: CO3 sulfate: SO4 sulfite: SO3
Silicate: SiO3 phosphate: HPO4 selenite: SeO4
Manganese: manganous molybdate tetraoxide: lead molybdate tetraoxide: lead trioxide.
Tungstate: WO4 uranium: UO4 stannate: SnO3
Ferrate: FeO4 chromate: CrO4 dichromate: Cr2O7
-3 valence
Phosphate: PO4 phosphite: PO3 hypophosphite
Urea is an organic compound composed of carbon, nitrogen, oxygen and hydrogen, also known as urea. Its chemical formula is con2h4, nh22co or cn2h4o, its molecular weight is 60, and its international drug name is urea. The appearance is white crystal or powder. It is the product of protein metabolism in animals and is usually used as nitrogen fertilizer for plants. Urea is synthesized in the liver and is a nitrogen-containing metabolite excreted by mammals. This metabolic process is called urea cycle. Urea is the first organic compound obtained by artificial synthesis of inorganic substances. The theory of vitality was overthrown. Urea is a kind of high concentration nitrogen fertilizer, which belongs to neutral quick-acting fertilizer and can also be used to produce a variety of compound fertilizers. No harmful substances remain in the soil, and long-term application has no adverse effects. Animal husbandry can be used as feed for ruminants. However, when the granulation temperature is too high, a small amount of biuret, also known as biuret, will be produced, which will inhibit crops. China stipulates that the biuret content of urea for fertilizer should be less than 0.5.
Urea is a kind of high concentration nitrogen fertilizer, which belongs to neutral quick-acting fertilizer and can also be used to produce a variety of compound fertilizers. No harmful substances remain in the soil, and long-term application has no adverse effects. Animal husbandry can be used as feed for ruminants. However, when the granulation temperature is too high, a small amount of biuret, also known as biuret, will be produced, which will inhibit crops. China stipulates that the biuret content of urea for fertilizer should be less than 0.5. When the biuret content exceeds 1 1, it cannot be used as seed fertilizer, seedling fertilizer and foliar fertilizer, and the urea content in other application periods should not be too high or too concentrated. Urea is an organic nitrogen fertilizer, which can only be absorbed and utilized by crops after being hydrolyzed into ammonium carbonate or ammonium bicarbonate by urease in soil. Therefore, urea should be applied about 7 days before the fertilizer requirement period of crops. Urea should be applied 7 days before the fertilizer demand period of crops.